The nano-electronic technology is reckoned as the micro-electronic technological core of future new era as it mainly has working current of the nano-electronic component with quantum effect is in the range of several to several tens of electron such that its energy consumption in working operation being very low; Comparing with current micro-electronic component in the semiconductor, not only its energy consumption can be substantially reduced but also the pulse frequency (namely operation speed) is relatively enhanced; Wherein, Single Electron Transistor (SET) is considered as the potential core in the next generation of microprocessor, of which the main operational basis is on the physical effect of Coulomb Blockade Effect and Single Electron Tunnel Effect.
In the middle age of the 20th century, both of the physical effect of Coulomb Blockade Effect and Single Electron Tunnel Effect were already theoretically expected, and the Coulomb Blockade Effect was one of important physical phenomena observed by the solid physics in 1980; When a physical system reduced to reach the nano scale, the charging and discharging process in such system will becomes discrete, namely quantumized. The Charging Energy (Ec) for charging an electron is [e2/2C], where, e is the electric charge of an electron, C is electric capacitance of such physical system; If the smaller is the C, then the greater is the Ec, hence it being called Coulomb Blockade Energy; Under such circumstance of the system, the charging and discharging electron can merely transmitted in one by one electron manner instead of collective group manner; the feature of single electron transmission in individual manner for the nano-scale system is called Coulomb Blockade Effect. Besides, if two quantum points are connected by a “Tunnel Junction” with a “Tunnel Barrier” in between, then a single electron passes from one quantum point through the Tunnel Barrier and reaches the other quantum point is called “Quantum Tunneling Effect”. In order to enable an electron tunnel from one quantum point through the Tunnel Barrier and reach the other quantum point, the energy of that electron (eV) must overcome the (Ec) of that electron, namely (eV)>(e/2C), where, C is the electric capacitance of the Tunnel Junction between both of the quantum points. Up to the 80 years of the post 20th century, people can then successfully fulfill the utilization these effects in the circuit of electronic component under super low temperature; that is later than the theory of which for over several decades; the reason is that the human technology is neither mature enough to form a very tiny electrode nor to precisely position those electrodes. The direct application of the Coulomb Blockade Effect and Single Electron Tunnel Effect is the design and fabrication of the Single Electron Transistor (SET). The characteristic advantage of the SET component is low energy consumption, high temperature sensitivity and easiness of integration so that it is reckoned as one of the most promising new nano components after the micro electronic components.
Please refer to FIG. 1, the fundamental circuit diagram of the Single Electron Transistor (SET), which had been already published, is a triode of source electrode S, drain electrode D and gate electrode G as well as an island electrode I, which locating between said source electrode S and drain electrode D; For said island electrode I, its electric capacitance is very small and its size is in nano scale relatively and further has Coulomb Blockade Effect of quantum dot QD and Tunnel Junctions at both ends of which; The characteristic of that structure is on the discrete energy level inside of the quantum point so that the electron can only tunnel from the source electrode S quantum point to the drain electrode D quantum point under the condition of lining up the Fermi level of the source electrode S quantum point and the drain electrode D quantum point with the energy level in the quantum point; Thereby, the tunneling electron number for each time can be controlled even up to optimal manner of only one single electron tunneling through each time; Hence, the total performance and yield of the SET is effected by the d1, d2 and d3 as well as size of itself, where, d1 is the distance between the source electrode S and the island electrode I, d2 is the distance between the drain electrode D and the island electrode I, and d3 is the distance between the gate electrode G and the island electrode I; For current technology level, it is hard to achieve foregoing requirements; The high fabricating cost other than the technical difficulty aforesaid is the primal reason that SET is still not adopted in mass production by semiconductor and electronics industries.
As further shown in FIG. 2 through FIG. 4, the nano-structure is produced from conventional nano-lithography. The fabricating steps are as below: (A): First layout the expected nano pattern Q on the photomask M, then put said photomask M on the top surface of the substrate 1, which being spread with photo-resist 2 (as shown in the FIG. 2); (B): Pass light beam e through said nano pattern Q on said photomask M so as to have same pattern as said nano pattern Q on said photo-resist 2, which spreads on said substrate 1, by exposure and development to define the nano-aperture 3 structure (as shown in the FIG. 3); (C): By means of deposit source device 30, directly deposit deposit material B of gas molecule or atom state on the surroundings and bottom of said nano-aperture 3 (as shown in view X and view Y of the FIG. 4); And (D): Finally, selectively remove said photo-resist 2 by solution, thereby forming a nano quantum dot 4 structure on the surface of said substrate 1 (as shown in view Z of the FIG. 4). Wherein, the conventional process aforesaid being confined to the precision limit of the existing photolithography such that the current best precise nano-scale can only reach 60˜65 nm; Hence, the nano-scale of said nano-aperture 3 from photomask M of pattern transferring photolithography is over 60 nm; Thereby, the nano-scale of said nano quantum dot 4 fabricated from these equipment is also over 60 nm relatively; Thus, the physical size limit of said conventional nano-devices of nano-structure is still in the range of over 60 nm; Therefore, how to breakthrough this bottleneck such that making the nano-scale of nano-aperture 3 be smaller becomes the impending crucial technical tough question of all experts in various fields; The solution being subject to the industrial practical feasibility in mass production and cost-effective economical principle so that the choice of means in technical breakthrough becomes more difficult; The scientists who understand the nano-science and the experts who familiarize with nano-technology are all aware of the benefits of working out the devices being smaller than 10 nm or even 1˜2 nm, but none of better solution or effective technical breakthrough is proposed, announced or applied.